Add markdown cache columns to the database, but don't use them yet

This commit adds a number of _html columns and, with the exception of Note,
starts updating them whenever the content of their partner fields changes.

Note has a collision with the note_html attr_accessor; that will be fixed later

A background worker for clearing these cache columns is also introduced - use
`rake cache:clear` to set it off. You can clear the database or Redis caches
separately by running `rake cache:clear:db` or `rake cache:clear:redis`,
respectively.

1 files changed, 7 insertions, 0 deletions

diff --git a/spec/factories/projects.rb b/spec/factories/projects.rb
index 873d3fcb5af..331172445e4 100644
--- a/spec/factories/projects.rb
+++ b/spec/factories/projects.rb
@@ -9,6 +9,9 @@ FactoryGirl.define do
     namespace
     creator
 
+    # Behaves differently to nil due to cache_has_external_issue_tracker
+    has_external_issue_tracker false
+
     trait :public do
       visibility_level Gitlab::VisibilityLevel::PUBLIC
     end
@@ -92,6 +95,8 @@ FactoryGirl.define do
   end
 
   factory :redmine_project, parent: :project do
+    has_external_issue_tracker true
+
     after :create do |project|
       project.create_redmine_service(
         active: true,
@@ -105,6 +110,8 @@ FactoryGirl.define do
   end
 
   factory :jira_project, parent: :project do
+    has_external_issue_tracker true
+
     after :create do |project|
       project.create_jira_service(
         active: true,